Viscose spinning process



United States Patent 2,853,360 VISCOSE SPINNING PROCESS Byron A. Thumm, Prospect Park, Pa., assignor to American Viscose Corporation, Philadelphia, Pa., a corporation of Delaware No Drawing. Application November v3, 1954 Serial No. 466,674

6 Claims. (CI. 18-54) This invention relates to the production of shaped bodies of regenerated cellulose from viscose and more particularly to filaments and fibers of regenerated cellulose from viscose.

In the conventional methods of producing shaped bodies of regenerated cellulose from viscose, a suitable cellulosic material such as purified cotton linters, wood pulp, mixtures thereof, and the like is first converted to an alkali cellulose by treatment with a caustic soda solution and after shredding the treated cellulose material, it is allowed to age. The aged alkali cellulose is then converted to a xanthate by treatment with carbon disulfide. The cellulose xanthate is subsequently dissolved in a caustic soda solution in an amount calculated to provide a viscose of the desired cellulose and alkali content. After filtration, the viscose solution is allowed to ripen and is subsequently extruded through a shaped orifice into a suitable coagulating and regenerating bath.

In the production of shapedbodies such as filaments, the viscose solution is extruded through aspinneret into a coagulating and regenerating bath consisting of an aque ous acid solution containing zinc sulfate. The filament may subsequently be passed through a hot aqueous bath where it is stretched to improve its properties such as tensile strength. The filament may then be passed through a dilute aqueous solution'of sulfuric acid and sodium sulfate to complete the regeneration of the cellulose, in case it is not completely regenerated upon leaving the stretching stage. The filament ,is subsequently subjected to washing, purification, bleaching, possibly other treating operations and drying, being collected either before or after these treatments.

The filaments as formed by the conventional methods, consist of a skin or outer'shell portion and a core portion with a sharp line of demarkation between the .two. The cross-section of the'filarnents exhibits a very irregular or crenulated 'exteriorsurface when even small amounts of zinc salts or certain other polyvalent metal saltssare present in thespinning bath. The skin and core .portions of 'the filament representdiiferences in structure and these different portions possess different swelling. and staining characteristics, the latter permitting a ready identification of skin and core. The sharply 'irregularand crenulated surface structure has a relatively low abrasion resistance and readily picks up foreign particles such as dirt. Although the coreportionpossesses 'a re'latively'high tensile strength, it has a low abrasion resistance and a'low flex-life, is subject to fibrillation "and is re'lativelystiff.

It has now been discovered that-the presence of small amounts of water-soluble alkylene oxide adducts of morp'holine in viscose and in the'spinning bath results in "the productionof shaped bodies of regenerated-cellulose such :as filaments, "films, sheets and the like composed of all skin .and :having :improved properties and characteristics providing that'the amount of theiadduct-isrmaintained with certain-limits .andtthetcomposition f'QfTthe :spinn'ing bath is maintained within .certain composition limits which will be defined hereinafter. The most readily distinguishable characteristics as compared to conventional filaments include a smooth, non-crenulated surface and the filaments consistentirely of skin.

This invention contemplates the use of alkylene oxide adducts of morpholine'havingfrom 1 to about 50.or more alkylene oxide groups per molecule, preferably from 1 to about 20 alkylene oxide units per molecule of morpholine. It is obvious that for all practical purposes con sidering cost, ease of preparation, commercial availability and solubility in water, in alkali solutions and in acid solutions, the ethylene oxide adducts are preferred.

The production of all skin products requires that certain minimum amounts of the alkylene oxide adductbe in solution in the viscose and in the spinning bath. Therefore, the alkylene oxide adduct must 'have sufficient solubility to permit the minimum amount of the adduct .to :be dissolved in both the viscose and the spinning :bath. The adduct may be conveniently added to the viscose in the form of a solution in alkali or water and to the spinning bath in a solution of water or of the spinning bath. i

The term fadduct" closure and description and .designates an N-substituted morpholine formed by the reaction between an alkylene oxide and morpholine wherein the alkylene oxide or the polyoxyalkylene chain replaces the hydrogen atom attached to the nitrogen atom. These adducts or reaction products may be-represented 'by the following structural formula /'QHQC H2 V 0 N- (alk-ylene oxlde),.H

O zCHz wherein n is from 1 to about 50. It is not necessary to employ individual specific compounds of the type described and the reaction product which may consist of a mixture of specific compounds, the average alkylene oxide content per molecule of morpholine being within the stated range are satisfactory.

The amount of the adduct which is incorporated in the viscose "must be at least about 0.25% by weight of {the cellulose in the viscose and may vary up to about 4% preferably, the amountvaries-from-0.5 to 2%. Lesser amounts do not result in the production of products consisting entirely of skin and greater amounts aflect adversely the physical properties of the products. Amounts withinthe preferred range are most effective in enhancing the characteristics and properties of the products. "The adduct of morpholine may be added at any desired stage in the production-of the viscose such as in the preparation of the refined wood pulp for the manufacture of viscose, before or duringthe shredding of the alkali cellulose, -to the -xanthated cellulose while it is being dissolved inthe caustic solution or to the viscose solution before ,or after filtration. The adduct is preferably added after the cellulose xanthate has been dissolved in the caustic solution and prior tofiltration.

The viscose may contain from about 6% to about 8% cellulose, the particular source of the cellulose being 'se "lected for the ultimate use of the regenerated cellulose product. The caustic soda content may be from about 4% to about 8% and the carbon disulfide content may be from about 30% to about 50% based upon the weight of the cellulose. The modified viscose, that is, a viscose containing 'the small amount of adduct, may have a salt 'test above about '7 and preferably above about '8 at the time of spinning or extrusion. The term salt test as used herein refers to the conventional sodium chloride salt test.

eln order itO: obtain the improvements enumerated hereinbefore itz is essential that the composition of the spinning bath be maintained within a well defined range and that is used herein to simplify the .dis-

.slubbing point.

3 the .spinning bath contain in solution at least about 0.01% of the adduct. The presence of the alkylene oxide adducts of morpholine in the viscose and in the spinning bath combined with these limited spinning baths results in the production of yarns of improved properties such as high tenacity, high abrasion resistance, high fatigue resistance and consisting of filaments composed entirely of skin.

Generically and in terms of the industrial art, the spinning bath is a low acid-high zinc spinning bath to which is added the adduct of morpholine in amounts of from about 0.01% to about 0.1%, preferably about 0.05%. The bath should contain from about to about 25% sodium sulfate and from about 3% to about zinc sulfate, preferably from 15% to 22% sodium sulfate and from 4% to 9% zinc sulfate. Other metal sulfatessuch as iron, manganese, nickel and the like may be present and may replace some of the Zinc sulfate. The temperature of the spinning bath may vary from about 25 C. to about 80 C., preferably between about 45 C. and about 70 C. In the production of the all skin type filaments, the temperature of the spinning bath is not critical, however, as is well known in the conventional practice in the art, certain of the physical properties such as tensile strength vary directly with the temperature of the spinning bath. Thus, in the production of filaments for tire cord purposes in accordance with the method of this invention, the spinning bath is preferably maintained at a temperature between about 55 C. and 65 C. so as to obtain the desired high tensile strength. The acid content of the spinning bath is balanced against the composition of the viscose. The lower limit of the acid concentration, as is well known in the art, is just furic acid result in the production of products having skin and core. A lowering of the amount of adduct of morpholine, the lowering of the caustic soda content or the lowering of the salt test of the viscose reduces the maximum permissible acid concentration for the production of all skin filaments. It has been determined that the maximum concentration of acid which is permissible for the production of all skin products is about 8.5%.

The presence of the adducts of morpholine in the viscose and spinning bath retards the coagulation and, therefore, the amount of adduct employed must be reduced at high spinning speeds. Thus, for optimum physical characteristics of an all skin yarn formed from a viscose as above and at a spinning speed of about 50 above the slubbing point, that is, the concentration at a which small slubs of uncoagulated viscose appear in the strand as it leaves the spinning bath. For commercial operations, the acid concentration of the spinning bath is generally maintained about 0.4% to 0.5% above the For any specific viscose composition, the acid concentration of the spinning bath must be maintained above the slubbing point and below the point at which the neutralization of the caustic of the viscose is sufiiciently rapid to form a filament having a skin and core.

There is a maximum acid concentration for any specific viscose composition beyond which the neutralization is sufficiently rapid to produce filaments having a skin and core. For example, in general, the acid concentration of the spinning baths which are satisfactory for the production of the all skin products from a 7% cellulose, 6% caustic-viscose and containing the adducts of morpholine lies between about 5% and about 8%. The acid concentration may be increased as the amount of adduct is increased and also as the salt test of the viscose is increased. There is an upper limit, however, for the acid concentration based upon the amount of modifier and the concentration of caustic in the viscose. All skin products cannot be obtained if the acid concentration is increased above the maximum value although the amount of the adduct of morpholine is increased beyond about 4% while other conditions are maintained constant. Increasing the caustic soda content of the viscose beyond about 8% is uneconomical for commercial production methods. For example, a viscose containing about 7% cellulose, about 6% caustic soda, about 41% (based on the weight of cellulose) carbon disulfide, 1% (based on the weight of cellulose) of an ethylene oxide adduct of morpholine containing about 20 ethylene oxide units per molecule and having a salt test of about 10 when extruded into spinning baths containing 16 to 20% sodium sulfate, 4 to 8% zinc sulfate, 0.05% of the same ethylene oxide adduct of morpholine and sulfuric acid not more than about 7.8%, results in the production of all skin filaments. Lesser amounts of sulfuric acid may be employed. Greater amounts of sulmeters per minute, the adduct is employed in amounts within the lower portion of the range, for example, about 0.5 The determination of the specific maximum and optimum concentration of acid for any specific viscose, spinning bath and spinning speed is a matter of simple experimentation for those skilled in the art. The extruded viscose must, of course, be immersed or maintained in the spinning bath for a period suificient to eifect relatively complete coagulation of the viscose, that is, the coagulation must be sufiicient so that the filaments will not adhere to each other as they are brought together and withdrawn from the bath.

In the production of filaments for such purposes as the fabrication of tire cord, the filaments are preferably stretched after removal from the initial coagulating and regenerating bath. From the initial spinning bath, the filaments may be passed through a hot aqueous bath which may consist of hot water or a dilute acid solution and may be stretched from about 70% to about 120%, preferably between and Yarns for other textile purposes may be stretched as low as 20%. The precise amount of stretching will be dependent upon the desired tenacity and other properties and the specific type of product being produced. It is to be understood that the invention is not restricted to the production of filaments and yarns but it is also applicable to other shaped bodies such as sheets, films, tubes and the like. The filaments may then be passed through a final regenerating bath which may contain from about 1% to about 5% sulfuric acid and from about 1% to about 5% sodium sulfate with or without small amounts of zinc sulfate if regeneration has not previously been completed.

The treatment following the final regenerating bath, or the stretching operation where regeneration has been completed, may consist of a washing step, a desulfurizing step, the application of a finishing or plasticizing material and drying before or after collecting, or may include other desired and conventional steps such as bleaching and the like. The treatment after regeneration will be dictated by the specific type of shaped body and the proposed use thereof.

Regenerated cellulose filaments prepared from viscose containing the small amounts of the water-soluble alkylene oxide adducts of morpholine and spun in the spinning baths of limited acid content and containing the adduct of morpholine have a smooth or non-crenulated surface and consist substantially entirely of skin. Because of the uniformity of structure throughout the filament, the swelling and staining characteristics are uniform througohut the cross-section of the filament. Filaments produced pursuant to this invention and consisting entirely of skin have a high toughness and a greater flexing life than filaments as produced according to prior methods which may be attributed by the uniformity in skin structure throughout the filament. Although the twisting of conventional filaments, as in the production of tirev cord, results in an appreciable loss of tensile strength, there is appreciably less loss in tensile strength in the production of twisted cords from the filaments consisting entirely of skin. Filaments prepared from viscose contain- 'ing the alkylene oxide adducts of morpholine have ahigh tensile strength as compared to normal regenerated cellulose filaments, have superior abrasion and fatigue resistance characteristics and have a high flex-life. Such filaments are highly satisfactory for the production of cords for the reinforcement of rubber products such as pneumatic tire casings, but the filaments are not restrictedto such uses and may be used for other textile applications.

The invention may be illustrated by reference to the preparation of regenerated cellulose filaments from a viscose containing about 7% cellulose, about 6% caustic soda, and having a total carbon disulfide content of about 41% based on the weight of the cellulose. The viscose solutions were prepared by xanthating alkali cellulose by the introduction of 36% carbon disulfide based on the weight of the cellulose and churning for about 2% hours. The cellulose xanthate was then dissolved in caustic soda solution. An additional carbon disu'lfide was then added to the mixer and the (mass mixed for about one hour. The desired amount of an ethylene oxide adduct of morpholine was added to the solution and mixed for about /2 hour. The viscose was then allowed to ripen for about 30 hours at 18 C.

Example 1 Approximately 1% (based on the weight of the cellulose) of an ethylene oxide adduct of morpholine containing 1 ethylene oxide unit per molecule (N-beta-hydroxy- :ethylmorpholine or 4-rnorpholine ethanol) was added to andincorporated in the viscose as described above. The

viscose employed .in the spinning of filaments had a salt 'test of 9.8. The viscose was extruded through a spinneret to form a 210 denier, 120 filament yarn at a rate of about 22 meters per minute. The coagulating and regenerating bath was maintained at a temperature-of about 60 C. and contained 7.3% sulfuric acid, 8.2% zinc sulfate, 18% sodium sulfate and 0.05% of the ethylene oxide adduct of morpholine. The yarn was stretched about 90% while passing through a hot water bath at 95 C. The'yarn was collected in a spinning box, washed free of acids and salts and dried.

The individual filaments have a smooth, non-crenulated exterior surface and consist entirely of skin, no core being detectable at high magnification (e. g. 1500X). The filaments of a control yarn spun with the same viscose but without the addition of the modified agent and spun under the same conditions, exhibit a very irregular and serrated surface and are composed of about 75% skin and the balance core with a sharp line of demarkation between the skin and core. Other physical properties are set forth in the table which follows the examples.

Example 2 To a viscose as described above, there was added 2% of an ethylene oxide adduct of morpholine containing 20 ethylene oxide units per molecule (a 4-morpholinepoly (oxyethylene)ethanol). The viscose had a salt test of 8.2 and was spun into a 210 denier, 120 filament yarn by extrusion into a spinning bath containing 7.6% sulfuric acid, 8.6% zinc sulfate, 20% sodium sulfate, and 0.05 of an ethylene oxide adduct of morpholine containing 20 ethylene oxide units per molecule. The bath was maintained at 60 C. and the extrusion rate was about 22 meters per minute. The filaments were subsequently passed through a hot water bath at 95 C. and stretched about 48%. The yarn was collected in a spinning box, washed free of acids and salts and dried.

The individual filaments were readily distinguishable from control filaments in that they havea smooth, noncrenulated surface and consist entirely of skin while the control filaments have a very irregular and serrated surface and consist of about 75% skin and the balance core with a sharp line of demarkation between the skin and core. Other physical properties are set forth in the table which follows the examples.

6 Example 3 As a control for the foregoing examples, a viscose solution, prepared as described above, having a salt test of 10 was spun into a 210 denier, 120 filament yarn by extrusion into a bath containing 7.6% sulfuric acid, 8% zinc sulfate and 18% sodium sulfate. The bath was maintained at a temperature of about 61 C. The extrusion rate was about 22 meters per minute. The water bath was maintained at a temperature of about 95 C. and the filaments were stretched 82% while passing through the hot water. The yarn was collected in a spinning box, washed free of acid and salts and dried.

The individual filaments have a very irregular and serrated surface and consist of about 75% skin .and the balance core with a sharp line of demarkation between the skin and the core. Other characteristics are set forth in the table which follows:

Although the tenacity and elongation are the only properties set forth, they have been chosen because of the ease and simplicity with which such properties may be determined. In some instances, products made in accordance with this invention do not exhibit large or great improvements in tenacity and elongation, however, the products consist of a smooth-surfaced, all skin structure and possess improved abrasion resistance, flex-life and other properties as disclosed hereinbefore.

One of the properties of viscose rayon which has limited its uses is its relatively high cross-sectional swelling when wet with water, this swelling amounting to from about 65% to about for rayon produced by conventional methods. Rayon filaments produced in accordance with the method of this invention have an appreciably lower cross-sectional swelling characteristic, the swelling amounting to from about 45% to about 60%.

The modifier of this invention may be added to'any desired viscose such as those normally used in industry, the specific viscose composition set forth above, being merely for illustrative purposes. The alkylene oxide adduct of morpholine may be added at any desired stage in the production of the viscose and may be present in the cellulosic raw material although it may be necessary to adjust the amount present to produce a viscose having the proper proportions of the adduct at the time of spinning.

The term skin is employed to designate that portion of regenerated cellulose filaments which is permanently stained or dyed by the following procedure: A microtome section of one or more of the filaments mounted in a wax block is taken and mounted on a slide with Meyers albumin fixative. After dewaxing in xylene, the section is placed in successive baths of 60% and 30% alcohol for a few moments each, and it is then stained in 2% aqueous solution of Victoria Blue BS conc. (General Dyestuffs Corp.) for l to 2 hours; At this point, the entire section is blue. By rinsing the section first in distilled Water and then in one or more baths composed of 10% water and dioxane for a period varying from 5 to 30minutes depending on the particular filament, the dye is entirely removed from the core, leaving it restricted to the skin areas.

While preferred embodiments of the invention have been disclosed, the description is intended to be illustrative and it is to be understood that changes and variations 7 may be made without departing from the spirit and scope of the invention as defined by the appended claims.

I claim:

1. In a method of producing shaped bodies of regenerated cellulose consisting substantially entirely of skin, the step which comprises extruding a viscose containing from about 0.25% to about 4%, based on the weight of the cellulose in the viscose, of a water-soluble morpholine derivative into an aqueous spinning bath containing from about 10% to 25% sodium sulfate, from about 3% to zinc sulfate, at least about 0.01% of a water-soluble morpholine derivative and sulfuric acid, the sulfuric acid content of the spinning bath exceeding the slubbing point but not evceeding about 8.5%, the morpholine derivative being selected from the group consisting of Water-soluble compounds and mixtures of water-soluble compounds represented by the formula C H2 C H2 0 N -(alkylene oxide) "H 0 Hg 0 H3 wherein n is from 1 to about 50.

2. The step in the method as defined in claim 1 wherein the morpholine derivative is selected from the group consisting of water-soluble compounds and mixtures of water-soluble compounds represented by the formula set forth in claim 1 wherein the alkylene oxide is ethylene oxide and n is from 1 to 30.

3. In a method of producing shaped bodies of regenerated cellulose consisting substantially entirely of skin the steps which comprise adding to and incorporating in CHzCH:

O a N -(alkylene oxide) r.H

onion,

wherein n is from 1 to about 50.

4. The steps in the method as defined in claim 3 wherein the morpholine derivative is selected from the group consisting of water-soluble compounds and mixtures of water-soluble compounds represented by the formula set forth in claim 3 wherein the alkylene oxide is ethylene oxide and n is from 1 to 30.

5. An aqueous spinning bath for the production of regenerated cellulose products consisting substantially entirely of skin from viscose containing from about 10% to 25% sodium sulfate, from about 3% to 15% zinc sulfate, at least about 0.01% of a water-soluble morpholine derivative and up to about 8.5% sulfuric acid, the morpholine derivative being selected from the group consisting of water-soluble compounds and mixtures of water-soluble compounds represented by the formula CIEQC'H:

O N-(a-lkylene oxide) "H 0 H2O Ha wherein in is from 1 to about 50.

6. An aqueous spinning bath as defined in claim 5 wherein the morpholine derivative is selected from the group consisting of water-soluble compounds and mixtures of water-soluble compounds represented by the formula set forth in claim 5 wherein the alkylene oxide is ethylene oxide and n is from 1 to 30.

References Cited in the file of this patent UNITED STATES PATENTS 2,125,031 Polak -July 26, 1938 2,312,152 Davis Feb. 23, 1943 2,373,712 Schlosser Apr. 17, 1945 2,593,466 MacLaurin Apr. 22, 1952 

1. IN A METHOD OF PRODUCING SHAPED BODIES OF REGENERATED CELLULOSE CONSISTING SUBSTANTIALLY ENTIRELY OF SKIN, THE WHICH COMPRISES EXTRUDING A VIKSCOSE CONTAINING FROM ABOUT 0.25% TO ABOUT 4%, BASED ON THE WEIGHT OF THE CELLULOSE IN THE VISCOSE, OF A WATER-SOLUBLE MORPHOLINE DERIVATIVE INTO AN AQUEOUS SPINNING BATH CONTAINING FROM ABOUT 10% TO 25% SODIUM SULFATE, FROM ABOUT 3% TO 15% ZINC SULFATE, AT LEAST ABOUT 0.01% OF A WATER-SOLLUBLE MOROPHOLINE DERIVATIVE AND SULFURIC ACID, THE SULFURIC ACID CONTENT OF THE SPINNING BATH EXCEEDING THE SLUBBING POINT BUT NOT EVCEEDING ABOUT 8.5%, THE MORPHOLINE DERIVATIVE BEING SELECTED FROM THE GROUP CONSISTING OF WATER-SOLUBLE COMPOUNDS AND MIXTURES OF WATER-SOLUBLE COMPOUNDS REPRESENTED BY THE FORMULA 